Some wheel loaders are provided with a so-called hydro static transmission (HST) so that a hydraulic pump is driven by an engine output and a traveling hydraulic motor is driven by a hydraulic oil discharged from the hydraulic pump for the traveling of the vehicle.
Some wheel-type excavators, rough terrain cranes and the like employ a hydraulic mechanical transmission (HMT) system including a combination of HST and mechanical transmission (see, for instance, Patent Literature 2).
According to Patent Literature 2, hydraulic drive is automatically selected when a measured rotation speed of an output shaft is a predetermined value or less, whereas mechanical drive is automatically selected when the measured rotation speed is the predetermined value or more.